Add support for junit test result

[Evangelink]

Summary

Add support for junit test result.

Background and Motivation

The junit test result format is having way wider support than TRX and adding support would allow to integrate even further with ecosystem.

Proposed Feature

Add junit test result format.

[Youssef1313]

Keep in mind that xunit already shipped --report-junit. If we will use the same naming for our command-line option (to be aligned with --report-trx), it means that our package will not be compatible with xunit. So xunit users must stick with xunit's implementation of junit and cannot use ours.

I generally think that xunit should have shipped their junit reporter as a separate package.

[Evangelink]

It's probably not a problem. I mean we can sync with him to move the impl at platform level meaning there would be no need for his impl.

[fmaeseele]

Hi,
I have done most of the work in my company.
Please find the attached zip. I have a file diretory.build.props that defines a lot of things. So this requires more work to be integrated in a compliant way in testfx. Also, whatever inside the folder "platform" is internal in testfx, so if this code should be integrated, this folder should be removed and code adapted.
My code works just fine with our jenkins under the new Microsft Testing Platform.
It would be great if it could be natively integrated.

Note: The code was written considering my context with .net9 only. I didn't care of other .net versions.
Kind Regards,
François

JUnitReport.zip